Nickel electroplating composition and process

ABSTRACT

AN AQUEOUS ACIDIC NICKEL ELECTROPLATING BATH COMPRISING A COUMARIN COMPOUND AND AN EFFECTIVE LEVELING AND BRIGHTENING AMOUNT OF A BATH SOLUBLE 1-PROPYNOXY SULFONATE COMPOUND EFFECTIVE TO CARRY THE DEGRADATION PRODUCT OF COUMARIN.

US. Cl. 204-49 18 Claims ABSTRACT OF THE DISCLOSURE An aqueous acidic nickel electroplating bath comprising a coumarin compound and an effective leveling and brightening amount of a bath soluble l-propynoxy sulfonate compound effective to carry the degradation product of coumarin.

CROSS-REFERENCE TO RELATED CASES This case is a continuation-in-part of earlier filed U.S. Ser. No. 97,346, filed Dec. 11, 1970, now Pat. No. 3,719,-

BACKGROUND OF THE INVENTION This invention relates to an improved composition and process for the electrodeposition of metal and more particularly, it relates to improved composition and process for the formation of semi-bright electrodeposits of nickel and nickel alloys.

The use of coumarin as an additive in Watts type nickel electroplating baths, to produce soft, ductile, lustrous deposits with excellent leveling is well known. It is further known that the degree of leveling obtained is, in general, proportional to the concentration of coumarin in the plating bath, at least within concentration ranges of about 0.05 to 0.3 grams/liter.

Generally, however, the higher concentrations of conmarin which produce the best leveling, are not used, since the degradation products, which develop as the plating bath is electrolyzed, are formed at the rate proportional to the concentration of the coumarin which is present. Thus, a high concentration of coumarin gives the best leveling but also the highest rate of formation of degradation products, which products are generally melilotic acid. These degradation products are objectionable in that they can cause uneven dull gray areas which are not readily brightened by a subsequent bright nickel deposit; they reduce the leveling obtained from a given concentration of coumarin in the plating bath; and they can reduce the beneficial mechanical properties of the nickel electrodeposits.

Heretofore, it has been proposed to overcome the undesirable effects of the coumarin degradation products by the use of aldehydes, such as formaldehyde and chloral hydrate. This use of these aldehydes has, however, had certain limitations since high concentrations of these materials not only lower the ductility of the nickel electrodeposit but also appreciably reduce the leveling action of the coumarin. It has further been proposed in US. Pat. 3,414,491, to overcome the difiiculty encountered in using coumarin as an additive in nickel plating baths by including in the baths an ethylene oxide adduct of an acetylenic United States Patent 3,795,592 Patented Mar. 5, 1974 compound. Although this technique has been helpful in overcoming the problems encountered in the use of conmarin, these ethylene oxide adducts have produced problems of their own, particularly in their preparation. In this regard, it is to be noted that the safe inhalation level of ethylene oxide is relatively low, while mixtures of ethylene oxide and air are explosive in substantially all proportions. Additionally, the reaction to form these adducts must be carried out in a closed reaction vessel under pressure. There is, therefore, not only a considerable health and safety hazard in the production of these adducts, but also, undesirable cost and complexity in the equipment required.

SUMMARY OF THE INVENTION The invention relates to an improved composition and process for the electrodeposition of metal. More particularly, it relates to an improved composition and process for the formation of semi-bright electrodeposits of nickel and nickel alloys.

The present invention is directed to a plating bath for the electrodeposition of nickel, which comprises an aqueous solution of at least one nickel salt, a coumarin compound and brightening and leveling amounts of a l-propynoxy sulfonate compound.

DESCRIPTION OF PREFERRED EMBODIMENTS The present invention is directed to electroplating baths 7 which are aqueous acidic solutions containing one or more nickel salts. Typically, such baths may be prepared by dissolving nickel chloride and/or nickel sulfate and boric acid in water. Other nickel electroplating baths are those based on nickel formate, nickel sulfamate, nickel fluoroborate, or the like, as the nickel salt dissolved in the aqueous acidic solvent, may also be used. Additionally, the electroplating baths of the present invention may also contain one or more cobalt salts, of the same or similar type as the nickel salts have been indicated above. Where the electroplating baths used contain cobalt salts in addition to the nickel salts, the relative amount of these should be such that the resulting nickel-cobalt alloy electroplate produced contains at least about 80% nickel.

The nickel electroplating baths will contain effective brightening and/or leveling amounts of a l-propynoxy sulfonate compound. Preferably, the sulfonate will contain at least the following structure:

A preferred formula is as follows:

wherein R is a saturated alkylene or a hydroxy substituted saturated alkylene; R is a saturated alkylene, hydroxy substituted alkylene, or

The sulfonate preferred is present in the electroplating baths in very minute amounts within the range of 1 to about milligrams/liter, with the range from about 1 to 10 milligrams/ liter being preferred.

The above brightening and leveling compound will be employed in order to carry the degradation products of coumarin or coumarin derivatives.

It is to be appreciated, that with respect to the coumarin compound or material, in addition to coumarin itself, which is the most preferred, various substituted coumarins may also be used, such as 3-chlorocoumarin; 6- chlorocoumarin; 3-bromocoumarin, 3-acetyl coumarin; 7- hydroxy ethyl coumarin; S-methoxy coumarin; 7-ethoxycoumarin; 4,8-dimethyl coumarin; coumarin, 7-oxy propane sulfonic acid; and the like. Typically, the coumarin or substituted coumarin compounds are present in the electroplating baths in amounts within the range of about 0.025 to 0.5 grams/liter, with amounts within the range of about 0.05 to 0.3 grams/ liter being preferred.

Although the combination of the propargyl sulfonate compound with the coumarin compound overcomes the adverse elfects with the coumarin degradation products, and results in a consistently semi-bright deposit, it has been found that as the electroplating bath is used over extended periods of time, there is a gradual decrease in the leveling properties, for a givenconcentration of coumarin. This decrease in leveling is minimized by also including butyne diol in the bath, as an additional additive. In this manner, without increasing the coumarin concentration, a semibright nickel electrodeposit, having excellent leveling is consistently produced. Accordingly, in its most preferred embodiment, the electroplating bath of the present invention will typically contain from about 3 to 60 milligrams/ liter butyne diol, with amounts of from about 10 to 40 milligrams/liter being preferred.

It is to be noted, however, that although the amounts of the three additive components set forth above are typical of the amounts which may be used, this is not to say that amounts of these components which are outside of these ranges may not be used. Rather, it is intended that although for typical operations of the process of the present invention these amounts have been found to be pre ferred, in many instances, amounts which are both greater than and less than those which have been specificallyrecited will also produce satisfactory results. In this regard, it is to be appreciated that the specific amount of each of these additive components which is used will, of course, depend upon the particular amounts of the other components which are utilized.

In formulating the electroplating baths for use in the method of the present invention, an aqueous acidic solution is formed containing the desired nickel or nickel and cobalt salts. Typically, these electroplating baths will have a pH within the range of about 3 to 4.5 and, depending upon the particular nickel salts used, will contain the nickel salts in amounts within the range of about 200 to 400 grams/liter. Where cobalt salts are also present in the electroplating baths, these will typically be present in amounts within the range of about 10 to grams/liter, depending upon the particular salts used as well as the amount of the nickel salt which is present. In the most preferred plating baths, which will also contain boric acid, this material is desirable present in amounts within the range of about 30 to 60 grams/liter. Additionally, the additive components are included in the electroplating bath in the amounts which have been indicated hereinabove.

In the operation of the process of the present invention, the electroplating solutions will typically be used at a temperature within the range of about 45 to 63 degrees centrigrade. In general, agitation of the solution, either by air agitation, cathode rod agitation, mechanical agitation or the like, is preferred. Although with the electroplating baths of the present invention, semi-bright nickel electrodeposits are obtained over a wide current density range,

e.g., 5 to 150 amps per square foot the typical average current densities used. in the operation of the process are within the range of about 25 to 50 amps per square foot, with plating times of from about 10 to 60 minutes.

When operating in this manner, excellent semi-bright, ductile deposits of nickel and nickel-alloys containing at least nickel are obtained, which electrodeposits have excellent leveling characteristics. Moreover, it has been found that with the combined use of the l-propynoxy sulfonate compound, and the butyne diol, with the coumarin material, the adverse eifects of the melilotic acid degradation product of coumarin are overcome, without the formation of other adverse degradation products and maximum leveling is obtained even with high. concentrations of melilotic acid. Although normally, the coumarin degradation products will decrease the brightness and leveling obtained from a given concentration of coumarin, in a proportion to themelilotic acid concentration, thus requiring the use of greater amounts of coumarin to maintain the leveling, by the use of these two additional additives the concentration of coumarin may be maintained at a consistent level even when appreciable amounts of melilotic acid are present, while still obtaining excellent brightness and leveling results.

While various emabodiments have been described above, below are preferred embodiments. All percentages are percentages by weight and all temperatures are in degrees centigrade unless otherwise indicated.

Example A nickel plating bath was prepared containing the following components; nickel chloride 5.5 ounces per gallon; nickel sulfate 40 ounces per gallon; boric acid 5.5 ounces per gallon, melilotic acid, 3 grams/liter, pH 4.0; temperature F. with air agitation:

Various materials were added to counteract the effects of the coumarin degradation products. The concentrations used and the results are listed in the table.

As can be seen from the results in the table, the use of the l-propynoxy sulfonate compound gave surprising results in carrying the degradation products ofcoumarin thereby giving the bath a longer life in producing an acceptable semi-bright nickel deposit.

The l-propynoxy sulfonates of the present application can be prepared in a number of ways. Some ways are: Propargyl alcohol may be reacted with a sultone resulting in an alkylenegroup attached to the oxygen of the propargyl alcohol and a terminal sulfonate group attached to the alkylene group..The reaction can be described as follows: Propargyl alcohol can be reacted with equal molar amounts of propane sultone giving the following reaction:

STEP 1 HCEC-CHa-OH epichlorohydrin HCEC-cHIO- CH!CH0 H STEP 2 wherein n is from 1 to 4 inclusive.

4. f. as

5 TABLE Materials tested Results 100-200 mg./l. epichlorohydrin ad- Not effective.

duct of butyne diol (2 or more moles of epichlorohydrin/mole diol.

100-200 g./l. ethylene oxide adduct D of butyne diol (3 or more moles of oxide/ mole diol) 75 mg./l. methyl butynol ethylene D0.

oxide adduct (equimolar).

50 mg./l. methyl butynol Do.

10 mg./l. Surfynol 82 (trademark of Not very elfective.

Air Reduction for polyoxyethylene (very dark). derivatives of -octyne derivatives.

mg./l. Surfynol 104 Do.

10 mg./l. Surfyno1475 I Do.

5-30 mg./1. propylene oxide adduct Not very efiective.

of propargyl alcohol (4-20 moles of oxide/ mole alcohol).

5-30 mg./l. ethylene oxide adduct of Do.

propargyl (420 moles oxide/ mole alcohol).

150 mg./l. hexadienol -1 Do.

50 mg./l. 1 butene-3-yne Not effective.

50 mg./l. propargyl alcohol propane Excellent.

sulfonate.

100 mg./l. reaction product of bu- Not very effective.

tyne diol and epichlorohyd-rin-resulting product hydrolyzed (1.8 moles epichlorohydrin).

Varying amounts of dioX-alane butyne Not etfective.

diol adduct (equimolar ratio).

Butyne diol reacted with concentrated Do.

sulfuric acid.

100 mg./l. ethylene oxide adduct of D0.

methyl butynol (1.8 moles of oxide per mole of butynol). l

What is claimed is:

1. An aqueous acidic nickel electroplating bath comprising a coumarin compound and an effective leveling and brightening amount of a bath soluble l-propynoxy sulfonate compound effective to carry the degradation product of coumarin.

2. The bath of claim 1, wherein the sulfonate is of the formula;

wherein R is independently selected from the group consisting of saturated alkylene and hydroxy substituted saturated alkylene;

R is independently selected from the group consisting of saturated alkylene, hydroxy substituted saturated alkylene and wherein R is a hydroxy substituted alkylene or a saturated alkylene; M is a bath soluble cation; and x is'from 0 to 3 inclusive.

3. The bath of claim 2, wherein the sulfonate is present in an amount ranging from about 1 to about 20 milligrams/liter.

4. The bath of claim 2, wherein R is a saturated alkylene of up to 3 carbon atoms.

5. The bath of claim 2, wherein R is hydroxy substituted saturated alkylene of up to 3 carbon atoms.

6. The bath of claim 2, wherein x is 0.

7. The bath of claim 2, wherein x is 0 and R is C H 8. The bath of claim 2 wherein R is -CH CH(OH)- CH 9. The bath of claim 1, wherein butyne diol is present in an amount ranging from about 10 to 40 mg./l.

10. A method of producing semi-bright nickel electrodeposits comprising passing an electric current from an anode to a cathode through an aqueous acidic solution of claim 1 for a period of time sufficient to form a semibright nickel deposit.

11. The method of claim 10, wherein the sulfonate is of the formula;

SOsM

wherein wherein 'R is a hydroxy substituted alkylene or a saturated alkylene; M is a bath soluble cation; and x is from 0 to 3 inclusive.

12. The method of claim 11, wherein R is a saturated alkylene of up to 3 carbon atoms.

13. The method of claim 11, wherein R is hydroxy substituted saturated alkylene of up to 3 carbon atoms.

14. The method of claim 11, wherein x is 0.

15. The method of claim 11, wherein x is 0 and R is --C H 16. The method of claim 11, wherein R is 17. The method of claim 10, wherein the sulfonate is present in an amount ranging from about 1 to about 20 milligrams/ liter.

18. The method of claim 10, wherein butyne diol is present in an amount ranging from 10 to 40 mg./l.

References Cited UNITED STATES PATENTS 3,089,888 5/1963 Mayhew et a1 204-49 X 3,111,466 11/1963 Foulke et al. 20'449 3,414,491 12/ 1968 Du Rose et al 204-49 3,699,016 10/1972 Beach ct al. 204-49 GERALD L. KAPLAN, Primary Examiner U.S. c1. X.R. 

